Trait django_query::ordering::Field

pub trait Field<R>: Clone {
    type Value;
    fn apply_sorter<V: Sorter<Self::Value>>(
        &self, 
        op: &V, 
        a: &R, 
        b: &R
    ) -> Ordering;
}

Something that can apply a Sorter to a member of a type.

By asking the type to apply the operator, we can avoid cloning potentially large objects in more complex cases of nesting. If we used Accessor directly for everything, which is a much simpler definition, there are some constructs that we cannot handle efficiently, because of nested comparisons within members of type Option, for example (i.e. in the case that a Foo is to be sorted by the a member of a contained object of type Option<Bar>.

Associated Types

type Value

Required methods

fn apply_sorter<V: Sorter<Self::Value>>(&self, op: &V, a: &R, b: &R) -> Ordering

Extract whichever member this Field obtains from R, from both a and b and apply op to the results.

Implementors

impl<R, F> Field<R> for F where
    F: Accessor<R> + ReferenceField, 

type Value = <F as Accessor<R>>::Value